Valid for:

N610

N670

N870

N870E

Embedded Integrator

Virtual Integrator

This White-paper describes the LAN synchronisation.

  1. LAN synchronisation
  2. Network requirements
  3. Distance between base stations

1. LAN synchronisation


If the DECT connection between base stations seems to be not reliable enough to permanently guarantee a stable DECT over the air synchronization, e.g., because they are separated by iron doors or a firewall, you can determine that synchronisation should take place via LAN. In this case you can switch to LAN synchronization where you also need to work with PTP master.


Advantage of LAN synchronization

  • No Synchronization levels needs to be configured.
  • When a base station fails (Not the LAN Master) it will not have any impact on the other base stations.

  • Fewer base stations required as the overlapping area of the base stations is smaller. The overlapping area for handset handover can be smaller, because neighbored base stations do not need to receive each other in stable error free quality, but they must still be able to detect each other for the process of dynamic channel selection.

Disadvantage of LAN synchronization

  • Base stations must be in the same network segment.
  • Precision Time Protocol (PTPv2), deviation must be lower then 500 ns (rms).
  • High reliable LAN network is needed, see below for the requirements.


LAN synchronisation can look to be more easy then DECT synchronisation, but the Customers network has to be very reliable and network knowledge is required. Gigaset offers the possibility to measure the delay/quality but we can not advise you how to configure your switches as we are not the experts for these switches.

In case of bad network quality, it can take some seconds before the synchronization is lost. When this happens, all active calls of this base station are disconnected. It can take up to some minutes before synchronization is active again.

Here an example how PTP synchronisation works, using the two-step method.

  1. The LAN sync master clock is at 11:00:00
  2. The slave clock is at 11:00:03, there is a 3 seconds offset

    We imagine a one-second delay to transfer the package from the LAN sync master to the slave

  3. Master sends a sync message at exactly 11:00:00 (T1 value)
  4. After the sync message, a follow-up message is send immediately (with T1 value)
  5. The T1 value is not in the sync message
  6. The follow-up message means, “The sync message you received was sent at the time specified in the T1 value”
  7. The slave stored the time it received the sync message as the T2 value. The local clock believes is it 11:00:04. There is a 4 second time difference. But as it does not know how long it takes to receive a message from the Master, it can not update the local clock.

    To correct itself, two values needs to be created:
    - The delay, how long does it take to receive the PTP messages from the master
    - The offset to update its clock

    delay = ((T2 - T1) + (T4 - T3)) / 2

    offset = ((T2 - T1) - (T4 - T3)) / 2

  8. After receiving the Follow-up message, the slave sends a Delay_Request message. The slave stores the time as T3 value

    Because of the one-second delay, the master receives it at 11:00:03, this is stored as T4 value
  9. The master replies immediately with a Delay_Response message that has the T4 value.

    The slave clock has now four timestamps


  • T1: 

Included in the follow-up message from the master clock: 11:00:00.

  • T2:

The time that the slave clock received the sync message: 11:00:04

  • T3:

The time that the slave clock send the Delay_Request message: 11:00:05

  • T4:

The time the master receives the Delay_Request message: 11:00:03

The slave can calculate the:

delay = ((11:00:04 - 11:00:00) + (11:00:03 - 11:00:05)) / 2 = (4 - 2) / 2 = 1 second

offset= ((11:00:04 - 11:00:00) - (11:00:03 - 11:00:05)) / 2 = (4 + 2) / 2 = 3 seconds


2. Network requirements

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To be able to use LAN synchronisation, consider the following network requirements:

Precision Time Protocol (PTPv2), deviation must be lower then 500 ns (rms)

Accuracy: How accurate the slave clock is to the master. Every clock, even an atomic clock, has some deviation from the actual time. The lower, the better.

Base stations must be in the same network segment

PTP messages are forwarded in a VLAN but not between VLANs

The less switch hops. the lower the transmission delay and its jitter will be.

Each switch in the network has to forward the PTP messages, this takes time and adds delay. (Indicated with the blue arrows)

The higher the bandwidth or quality of used switches is regarding packet delay and its jitter, the lower the packet delay and the lower the packet delay jitter will be.


Enhanced packet processing logics (like L3 switching or packet inspection) could have significant negative impact on the resulting packet delay jitter. If possible, they should be deactivated for the N870 base stations connected switch ports.


Significantly increased traffic load on a switch, in the range of the maximum throughput, could have significant negative impact on the packet delay jitter.


VLAN based prioritisation of LAN packets could be a fruitful measure to minimize packet delay and its jitter for N870 base stations.




3. Distance between base stations

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DECT synchronisation

Distance between DECT base is measured with the SPK and should be -65 / -70 dBm


LAN synchronisation

The DECT base must be able to see the neighbor base via the DECT protocol.

The visualization tool can be used to check this.